Radio communication system

ABSTRACT

A radio communication system wherein one or a consecutive plurality of sub-carriers at certain frequency intervals form sub-carrier groups each of which is assigned to a different user, the radio communication system including a radio communication apparatus; and a terminal configured to receive a notification for identifying control signal positions from the radio communication apparatus, wherein the terminal receives a control signal and a data signal according to the control signal positions identified by the notification.

CROSS REFERENCE TO RELATED APPLICATION

This present application is a continuation of U.S. patent applicationSer. No. 12/878,537, filed on Sep. 9, 2009, now pending, which is acontinuation of U.S. application Ser. No. 11/442,173 filed May 30, 2006,now issued as U.S. Pat. No. 7,949,307, which is based upon and claimsthe benefit of Japanese Patent Application No. 2006-18521, filed on Jan.27, 2006, the contents of each are herein wholly incorporated byreference. The present application also relates to U.S. application Ser.No. 13/018,645, filed Feb. 1, 2011, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a radio communication system,an, more particularly, to a radio communication system that uses anOFDMA (Orthogonal Frequency Division multiplexing Access) connectionmode and a base transceiver station apparatus using the same.

2. Description of the Related Art

Recently, an OFDMA (Orthogonal Frequency Division multiplexing Access)system is applied to a mobile communication system that is one form ofradio communication systems.

In the OFDMA, as shown in FIG. 1, for example, a 20 MHz band is dividedinto a plurality of consecutive 5-MHz sub-carriers, for example, in thefrequency direction, and each

Sub-carrier is assigned to a user of service to achieve user- orservice-multiplexing.

In FIG. 1, consecutive sub-carriers are assigned to four users 1 to 4.Since a plurality of consecutive frequencies is collectively assigned toa plurality of users, this multiplexing method may be referred to aslocalized OFDMA.

As shown in FIG. 2, the distributed OFDMA is also proposed to select oneor a consecutive plurality of sub-carriers at certain frequencyintervals to create sub-carrier groups, which are assigned to users.

In such a case, a radio channel used by each user is constituted by adata channel (DPDCH) and a control channel (DPCCH), which are mapped toone radio frame format. The frame format of the radio channel is fixed.

A configuration shown in FIG. 3 is a typical base transceiver stationconfiguration in the mobile radio system, which is the radiocommunication system using the OFDMA. A control signal on the controlchannel (DPCCH) from a control signal generating unit 30 and a datasignal on the data channel (DPDCH) from an upper layer are mapped to apredetermined format by a frame format generating unit 31.

The output from the frame format generating unit 31 is encoded by anencoding unit 32, is modulated by a modulating unit 33 in a modulationmode such as QPSK, is subjected to frequency conversion to a radiofrequency signal by a transmission radio unit 34, and is emitted from anantenna 35.

FIG. 4 is a configuration example of a transmission radio unit 34 and,particularly, is a configuration example of an OFDM radio unit. Theoutput of the modulating unit 33 is converted by an S/P converter 340 toa parallel signal. The parallel signal is subjected to an IFFT processby an inverse Fourier transform (IFFT) circuit 341 and is restored to aserial signal by a P/S converter 342. This serial signal is added withguard intervals GI, is converted to a radio frequency by a frequencyconverter 345, and is emitted from the antenna 35.

FIG. 5 is a configuration example of a terminal corresponding to theconfiguration of the base transceiver station of FIG. 3. A receivedsignal received by a reception antenna 40 is subjected to frequencyconversion to be a base band signal and is input to a demodulating unit42. The signal is subjected to a demodulating process corresponding tothe modulating unit 33 of the base transceiver station by thedemodulating unit 42 and is divided into the data and the control signalby a signal dividing unit 44.

On the other hand, in FIG. 5, received power is measured from a pilotsignal and the result thereof is sent to a channel estimating unit 46,etc. The channel estimating unit 46 estimates a propagation path, etc.from the measured power.

In this way, when the terminal performs the measurement of the receivedpower, the channel estimation, the power control, the adaptivemodulation control, etc. by receiving the pilot channel or pilot symbolincluded in the control channel (DPCCH), the intended control is norperformed accurately, unless the transmission quality is ensured at acertain level or more (e.g., an error rate of 1.0E to 2).

To ensure the transmission quality, the transmission power of thecontrol signal on the control channel (DPCCH) is made higher than thecase of the usual data transmission.

FIGS. 6A and 6B are diagrams for describing problems to be solved by thepresent invention. In FIGS. 6A and 6B, FIG. 6A shows a time-frequencydistribution of four-user sub-carriers mapped to a radio frame format.The frame format of the radio channel is fixed. Since the controlchannel (DPCCH) is control information necessary for communication, thetransmission quality thereof must be made higher than the data channel(DPDCH).

Therefore, as shown in a transmission power distribution of FIG. 6B,countermeasures are taken in a W-CDMA (Wideband Code Division MultipleAccess) system by making the transmission power of the control channel(DPCCH) higher than the data channel (DPDCH). From FIG. 6B, it isunderstood that the transmission power is made higher at the cycle ofthe control channel (DPCCH).

In this way, the transmission power of the control signal on the controlchannel is increased conventionally. As shown in FIGS. 3 and 4, sincethe OFMDA base transceiver station performs the IFFT, it is desirablethat the beginnings of the data for the users, i.e., the beginnings ofthe radio frames are identical.

If the beginnings of the radio frames are not identical, since thesignal process becomes complicated, the apparatus configuration and thecontrol are also complicated. Therefore, the beginnings of the radioframes must be identical.

However, if transmission for a plurality of users is performedconcurrently with the use of the fixed radio frame format as describedabove, the positions of the control channels (DPCCH) are identical (seeFIG. 6A). Therefore, since the transmission signal for each user isadded in the same phase in the OFDMA, a peak of the transmission poweris generated at the time of the transmission on the control channel(DPCCH) with high transmission power. For example, in FIG. 6B, P1 ispeak power at a time T1.

Consequently, a peak-to-average power ratio (PAPR) becomes a highervalue, which generates various disadvantages.

In general, the following problems are generated when the PAPR is ahigher value.

-   -   In the design of an amplifier of the radio apparatus, a margin        of the design must be made greater.    -   Since the peak output power becomes higher power, the efficiency        of the amplifier is deteriorated.    -   Since the peak output power becomes higher power, power        consumption is increased.

Because of these problems, it is important to constrain the PAPR to alower level. In the W-CDMA system, since the positions of the controlchannels are identical and a greater peak is generated in thetransmission power as described above, it is important to constrain thePAPR to a lower level.

For such problems, it is proposed to perform encoding with the use ofcodes with different code distances, which is one of an unequal errorprotecting method, to control such that transmission peak power of amulti-carrier modulation signal becomes a predetermined value or less(Japanese Patent Application Laid-Open Publication No. 2000-286818).

An invention described in Japanese Patent Application Laid-OpenPublications No. H11-154904 and 2005-57610 are an invention relating tothe transmission power/PAPR constraint.

An invention described in Japanese Patent Application Laid-OpenPublication No. H11-154904 is intended to reduce the peak-to-averagepower ratio by time-multiplexing the pilot signal and the data signal toform channels and to reduce the number of orthogonal symbols used forforming the channels. The invention described in Japanese PatentApplication Laid-Open Publication No. 2005-57610 is intended to sort theorder of generated diffusion codes randomly to determine the ordercorresponding to each of a plurality of users.

3GPP Contribution(R1-050604), Sophia Antipolis, France, 20-21 Jun., 2005proposes a format that is dispersedly arranged to be a common controlchannel and this is applied to the common control channel and high-speedusers in scheduling dependent on a frequency channel.

However, in the invention described in Japanese Patent ApplicationLaid-Open Publication No. 2000-286818, since codes must be selected tovary the minimum code distances, the code selection is restrained.Japanese Patent Application Laid-Open Publication Nos. H11-154904 and2005-57610 do not refer to the increasing of the PAPR due to theaccumulation of the power of the control channel. Therefore, thedispersed arrangement is not indicated which is performed by payingattention to the control channel. Although 3GPP Contribution(R1-050604), Sophia Antipolis, France, 20-21 Jun., 2005 describes thatthe dispersed arrangement is performed such that the transmissioncharacteristics are improved at the time of high-speed movement, it isnot indicated that the dispersed arrangement is performed to reduce thePAPR.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to provide a methodof generating a frame format that can constrain the PAPR at a lowerlevel without limitation of the code selection.

In order to achieve the above object, according to a first aspect of thepresent invention there is provided a radio communication system witheach radio channel constituted by a control channel and a data channel,the radio communication system dividing a plurality of the radiochannels in a frequency direction for mapping to a radio frame format,wherein a control signal position on the control channel is controlledin the radio frame format for each user or service to reduce peaktransmission power or a peak-to-average power ratio of a radiocommunication apparatus. Preferably, from a plurality of the radio frameformats with the different control signal positions, the utilized radioframe format is selected at the time of connection setup. The utilizedradio frame format may be changed dynamically by notifying the utilizedradio frame format in advance. Scheduling may be performed forcontrolling the radio frame format based on channel quality informationfrom terminals. The scheduling may include a transmission order andselection of a modulation mode used at least for the transmission. Theterminals may be grouped for each utilized frame format and wherein thescheduling of the transmission order is performed correspondingly to thegroups.

In order to attain the above object, according to a second aspect of thepresent invention there is provided a radio communication apparatus in aradio communication system with each radio channel constituted by acontrol channel and a data channel, the radio communication systemdividing a plurality of the radio channels in a frequency direction formapping to a radio frame format, the radio communication apparatuscomprising a transmission power calculating unit that measures peaktransmission power or a peak-to-average power ratio (PAPR); and a frameformat controlling unit that controls the utilized radio frame formatbased on the calculation result of the transmission power calculatingunit.

In order to attain the above object, according to a third aspect of thepresent invention there is provided a radio communication apparatus in aradio communication system with each radio channel constituted by acontrol channel and a data channel, the radio communication systemdividing a plurality of the radio channels in a frequency direction formapping to a radio frame format, the radio communication apparatuscomprising a transmission power calculating unit that measures peaktransmission power or a peak-to-average power ratio (PAPR) of the entireapparatus; an individual transmission power calculating unit thatmeasures peak transmission power for each user or service, and a frameformat controlling unit that controls the utilized radio frame formatbased on the calculation results of the transmission power calculatingunit and the individual transmission power calculating unit. Preferably,the frame format controlling unit controls a control signal position onthe control channel in the radio frame format for each user or service.

In order to attain the above object, according to a fourth aspect of thepresent invention there is provided a radio communication apparatus in aradio communication system with each radio channel constituted by acontrol channel and a data channel, the radio communication systemdividing a plurality of the radio channels in a frequency direction formapping to a radio frame format, the radio communication apparatuscomprising a base band transmission power calculating unit that measurestransmission signal power of a base band to calculate transmission powerbased on the measurement result; and a frame format controlling unitthat controls the utilized radio frame format based on the calculationresult of the transmission power calculating unit.

In order to attain the above object, according to a fifth aspect of thepresent invention there is provided a connection setting method in aradio communication system with each radio channel constituted by acontrol channel and a data channel, the radio communication systemdividing a plurality of the radio channels in a frequency direction formapping to a radio frame format, the method comprising sending aconnection setting request from a radio network controller to a basetransceiver station; based on the connection setting request, the basetransceiver station selecting an unutilized radio frame format from aplurality of the radio frame formats with control signal positions onthe control channel controlled for each user or service, and notifying acorresponding terminal of the selected radio frame format; and theterminal notifying the base transceiver station of the completion of thesetting to start data transmission/reception with the use of thenotified radio frame format. The base transceiver station may performscheduling for controlling the radio frame format based on channelquality information from the terminal. The scheduling may include atransmission order and selection of a modulation mode used at least forthe transmission. The base transceiver station may group the terminalsfor each utilized frame format and perform the scheduling of thetransmission order correspondingly to the groups.

By applying the present invention, a peak of transmission power can bereduced. The PAPR can also be reduced. With the effects of the presentinvention, the operation point can be set higher without distorting theoutput of the amplifier and the power added efficiency of the amplifiercan be improved. Consequently, power consumption can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, aspects, features and advantages of thepresent invention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram for localized describing OFDMA;

FIG. 2 is a diagram for describing distributed OFDMA;

FIG. 3 is a block diagram of a base transceiver station configuration ina mobile radio system;

FIG. 4 shows a configuration example of a transmission radio unit and,specifically, a configuration example of an OFDM radio unit;

FIG. 5 shows a configuration example of a terminal corresponding to theconfiguration of the base transceiver station of FIG. 3;

FIGS. 6A and 6B are diagrams for describing problems to be solved by thepresent invention;

FIGS. 7A and 7B are diagrams for describing the principle of thesolution of the present invention;

FIG. 8 is a comparison diagram of the conventional case when a radioframe format is fixed in a radio channel used by each user and the casewhen the present invention is applied;

FIG. 9 is a block diagram of a configuration example of the basetransceiver station BTS in an OFDM system according to the firstembodiment;

FIG. 10 is a block diagram of a configuration example of a frame formatcontrolling unit of FIG. 9;

FIG. 11 is a block diagram of a configuration example of the terminal MSconnecting to the base transceiver station BTS;

FIG. 12 is a process sequence flowchart corresponding to the firstembodiment

FIG. 13 is a diagram for describing an example of the radio format;

FIG. 14 is a process sequence flowchart according to the secondembodiment;

FIG. 15 is a process sequence flowchart according to the thirdembodiment;

FIG. 16 is a block diagram of a configuration example of the basetransceiver station apparatus to which the fourth embodiment is applied;

FIG. 17 is a process sequence flow corresponding to the fourthembodiment;

FIG. 18 shows a configuration example of the base transceiver stationBTS corresponding to the fifth embodiment;

FIG. 19 is a process sequence flow of the fifth embodiment;

FIG. 20 is a diagram for describing the sixth embodiment;

FIG. 21 shows a configuration example of the base transceiver stationBTS corresponding to the eighth embodiment;

FIG. 22 shows a configuration example of the base transceiver stationBTS corresponding to the ninth embodiment;

FIG. 23 shows an example of a process flow of the ninth embodiment;

FIG. 24 shows a process sequence of the ninth embodiment;

FIG. 25 shows another process sequence of the ninth embodiment;

FIG. 26 shows a configuration example of the base transceiver stationcorresponding to the tenth embodiment;

FIG. 27 shows an example of a process flow of the tenth embodiment;

FIG. 28 shows a configuration example of the base transceiver stationBTS corresponding to the tenth embodiment;

FIG. 29 shows a configuration example of the base transceiver stationBTS corresponding to the twelfth embodiment;

FIG. 30 shows an example of a process flow corresponding to the twelfthembodiment;

FIG. 31 shows a configuration example of the base transceiver stationBTS corresponding to the thirteenth embodiment;

FIG. 32 shows an example of a process flow corresponding to thethirteenth embodiment;

FIG. 33 shows a configuration example of the base transceiver stationBTS corresponding to the fourteenth embodiment;

FIG. 34 shows a configuration example of the base transceiver stationBTS corresponding to the fifteenth embodiment; and

FIG. 35 shows a configuration example of the base transceiver stationBTS corresponding to the sixteenth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to the accompanying drawings. The embodiments of the presentinvention are for the purpose of understanding the present invention anddo not limit the technical field of the present invention.

Before describing the embodiments specifically, description will be madeof basic features of the present invention to facilitate theunderstanding.

As shown in FIGS. 7A and 7B that describe the principle of the solution,the present invention is characterized in that positions of controlchannels (DPCCH) in radio frame formats are arranged dispersedly foreach user or service.

In an example shown in FIGS. 7A and 7B, radio formats a to d are usedwhich disperse the positions of the control channels for each of users 1to 4.

Since this prevents the signal positions of the control channels (DPCCH)with high transmission power in a radio communication apparatus fromoverlapping, the peak transmission power can be reduced in a result ofuser-multiplexing. Specifically, as shown in FIG. 7B, for example, thepeak transmission power is reduced at time T1 to become P1.

In this way, the peak power can be reduced. For example, in a basetransceiver station acting as the radio communication apparatus, a peakfor each user is dispersed in the user-multiplexing. Therefore, it iseasily understood from a comparison diagram of the conventional case Iwhen a radio frame format is fixed in a radio channel used by each userand the case II when the present invention is applied as shown in FIG. 8that the peak power is reduced after multiplexing. Consequently, thePAPR is improved.

The position information of the control signal on the control channelcan be accommodated by notifying to a communication destination when aradio connection is set or by notifying to a communication destinationbefore changing.

Description will be made of each embodiment to which the features of thepresent invention are applied.

First Embodiment

In this embodiment, a radio format used at the time of connection setupis specified from a radio network controller (RNC) controlling a radiocommunication channel to a base transceiver station BTS by a terminal MSattempting to connect to the base transceiver station BTS under thecontrol of the radio network controller (RNC).

Description will be made of the process thereof.

FIG. 9 is a block diagram of a configuration example of the basetransceiver station BTS in an OFDM system according to a firstembodiment. FIG. 11 is a block diagram of a configuration example of theterminal MS connecting to the base transceiver station BTS.

FIG. 10 is a block diagram of a configuration example of a frame formatcontrolling unit 36 of FIG. 9. FIG. 12 is a process sequence flowchartcorresponding to the first embodiment.

An OFDMA system capable of four-user-multiplexing is taken as anexample. The radio formats used in this case are assumed to be fourtypes F1 to F4 shown in FIG. 13.

In a base transceiver station BTS under the control of one radio networkcontroller RNC, radio formats are searched which are used in threechannel already set. As a result, it is assumed that the format 1 (F1),format 2 (F2), and format 3 (F3) are used and the format 4 (F4) is notused.

The radio network controller RNC selects a format such that the peaktransmission power is reduced when a connection is set to the newterminal MS. That is, in the example shown in FIG. 13, when the format 4(F4) is not used and the format 4 (F4) is to be used, the format 4 (F4)is selected because the peak transmission power is not increased.

As shown in FIG. 12, the selected format 4 (F4) is notified from theradio network controller RNC to the base transceiver station BTS byformat information in a connection setting request (step S1).

As shown in FIG. 10 in detail, when the format information is notifiedfrom the radio network controller RNC, the frame format controlling unit36 in the base transceiver station BTS converts the format informationwith a format converting unit 360 to a format number, which is sent to aformat selecting/setting unit 361.

As shown in later embodiments, the format selecting/setting unit 361receives control information such as the peak transmission powerobtained based on output of a transmission radio unit 34 and uses aformat usage status and format detail information from a format usagestatus managing unit 362 and a format detail information setting unit363 to select a frame format and determine change timing.

The format detail information from the format detail information settingunit 363 is the number of the transmission data bits, the number ofcontrol information bits, and the orders (mapping method) thereof in aframe format, for example.

The format usage status managing unit 362 stores and manages which frameformat is used by which terminal MS.

As a result of the format selection as described above, the formatselecting/setting unit 361 delivers the format detail information to aframe format generating unit 31, converts the selected frame format to aframe format number with a frame format information converting unit 364,and sends the detail information to a control signal generating unit 37.

When receiving the control signal, the format detail information, andthe change timing information, the control signal generating unit 37generates a control signal based on a control information length (thenumber of bits) and the format number.

When receiving the format detail information, the frame formatgenerating unit 31 maps the control signal of the control channel andthe (transmission) data of the data channel to the radio frame inaccordance with the data and control signal lengths (the numbers ofbits) and the mapping method (FIG. 12, step S2).

The mapped data are encoded by an encoding unit 32, modulated by themodulating unit 33, subjected to frequency conversion to a radiofrequency by a transmission radio unit 34, and transmitted from anantenna 35 (step S3).

When the terminal MS receives this transmission, in the configuration ofthe terminal MS shown in FIG. 11, the signal received by an antenna 40is subjected to frequency conversion by a reception radio unit 41 and isdemodulated by a demodulating unit 42.

The result is decoded by a decoding unit 43 and the frame format controlsignal is extracted by a frame format extracting unit 51. The frameformat of the received signal is set by a frame format controlling unit50 based on the extracted frame format control signal.

The result is delivered to a signal dividing unit 44, a received powermeasurement unit 45, and the decoding unit 43 to perform the setting ofa receiving unit (step S4).

In the terminal MS, if the setting of the utilized frame format iscompleted in the receiving unit, the frame format controlling unit 50notifies a control signal generating unit 52 of the completion of thesetting and, when receiving this notification, the control signalgenerating unit 52 adds a setting completion signal to the controlsignal, which is delivered to a frame format generating unit 53.

In the frame format generating unit 53, the control signal and thetransmission data are mapped to the frame, modulated by a modulatingunit 55, subjected to frequency conversion to a transmission frequencyto adjust the transmission power, and transmitted from the antenna 40,and the completion of the setting is notified to the base transceiverstation BTS (step S5).

In the base transceiver station BTS, the completion of the setting mayalso be notified to the radio network controller RNC.

In this way, when receiving the setting completion notification, thebase transceiver station BTS or the radio network controller RNC can usethe set radio format to perform data communication (step S6).

In this case, the utilized frame format is determined before setting theconnection and the frame is used until the phone call is terminated.

The above process can reduce the peak power and improve the PAPR. In thedesign of the operation point of the amplifier, since the PAPR isreduced, the operation point does not have to be constrained to a lowerlevel to generate output without distortion. In other words, a marginfor the operation can be reduced without constraining the input signalpower at a lower level. That is, the operation point can be set at ahigher level.

Typically, the high power added efficiency of the amplifier is obtainedat the operation point that distorts the output. However, as a result ofthe above control according to the present invention, the operation canbe set at a higher level without distorting the output and the poweradded efficiency of the amplifier can be improved. As a result, powerconsumption can be reduced.

Although the localized OFDMA is described in the above description, theembodiment can be applied to a distributed OFDMA. The followingembodiments can also be applied to the distributed OFDMA unlessotherwise noted. The present invention is not limited to the applicationto the OFDMA.

Second Embodiment

Although the radio network controller RNC selects the utilized frameformat and notifies the base transceiver station BTS of the format inthe first embodiment, the base transceiver station BTS performs theselection in a second embodiment.

FIG. 14 is a process sequence flowchart according to the secondembodiment.

A connection setting request for one terminal MS is notified from theradio network controller RNC to the base transceiver station BTS (stepS1). As described in FIG. 13, the base transceiver station BTS selectsthe utilized format from the frame formats that can be selected suchthat the peak transmission power is reduced after the user-multiplexing(step S2 a). The result is notified to the terminal MS (step S3).

Subsequently, the processes same as the first embodiment (steps S4, S5)are performed for the communication (step S6). The selected frame formatis used until the phone call is terminated. In this way, the sameeffects as the first embodiment are generated.

Although the base transceiver station BTS selects the utilized frameformat in this description, in another aspect, the terminal MS canselect the utilized frame format and notify the base transceiver stationBTS of the result.

Third Embodiment

As is the case with the first and second embodiments, the utilized frameformat is selected in the base transceiver station BTS when setting theconnection. In consideration of the frame formats used by otherconnecting terminals MS, the utilized frame format is subsequentlychanged such that the transmission power peak is reduced.

It is assumed that a terminal MS selects the utilized frame format whensetting the connection as is the case with the first and secondembodiments and performs the communication. A connection request isassume to be notified from another terminal MS1 that is using the frameformat 3 because of handover, etc. However, it is assumed that yetanother terminal MS2 is using the frame format 3 and the frame format 1is not used.

In this case, to constrain the overall transmission power peak in thebase transceiver station, it is desirable that the terminal MS1 uses theframe format 1. Therefore, The utilized frame format of the terminal MS1is changed from 3 to 1.

Description will be made of the specific process of the third embodimentwith reference to a process sequence flowchart shown in FIG. 15. In theframe format controlling unit 36 of the base transceiver station BTSshown in FIG. 9, it is determined whether the utilized frame format mustbe changed or not (step S2 b). If it is determined that the frame formatmust be changed (step S2 b, Y), the utilized frame format is selectedsuch that the transmission power peak is reduced (step S2 a). The resultof the selection of the utilized frame format is notified to theterminal MS (step S3). The subsequent process steps S4 to S6 are thesame as the first embodiment.

It is assumed that a phone call is terminated on yet another terminalMS3. As a result, if it is determined that the transmission power peakcan be reduced by changing the utilized frame format, the same processas above is performed to change the frame format. The same process asthe first embodiment is performed subsequently.

If the utilized frame format is changed, the change, the change timing,and the utilized frame format after the change are also notified to thetransmission destination before the change timing, i.e., in advance.

As described above, by changing the utilized frame format, the peaktransmission power can be reduced as is the case with the firstembodiment.

Fourth Embodiment

FIG. 16 is a block diagram of a configuration example of the basetransceiver station apparatus to which a fourth embodiment is applied.FIG. 17 is a process sequence flow corresponding to the fourthembodiment.

Description will be made using the case that the utilized frame formatis instructed from the radio network controller RNC, which is anupper-layer apparatus. The utilized frame format may be selected by thebase transceiver station BTS (step S2 b).

When the utilized frame format is instructed from the radio networkcontroller RNC, the frame format controlling unit 36 checks anunutilized frame format from, for example, the four frame formats shownin FIG. 13 as is the case with the first embodiment, and the formatinformation (e.g., format number) is notified to the control signalgenerating unit 37 and the frame format generating unit 31 concurrently.

When notified the utilized frame format from the radio networkcontroller RNC, a scheduler unit 38 prioritizes the user transmissionbased on channel quality information CQI from terminals and transmitsthe data output from a transmission buffer 29 for each user in the orderfrom the highest priority (step S2 c). On this occasion, a modulationmode, etc. used for the transmission is selected and a transmission datasize is determined in consideration of the utilized frame format. Theencoding unit 32, the modulating unit 33, etc. are notified ofinformation such as the selected modulation mode and encoding rate.

When notified the utilized frame format from the radio networkcontroller RNC, the control signal generating unit 37 generates thecontrol signal from the format information notified from the frameformat controlling unit 36. The control signal is also generated andtransmitted with the use of the data size, the modulation mode, etc.notified from the scheduler unit 38 (step S3).

The same processes as the first embodiment (steps S4 to S6) aresubsequently performed. In this way, the same effects as the firstembodiment are generated.

Although the utilized frame format is fixed, the frame format can bechanged in accordance with the determination of the radio networkcontroller RNC or the base transceiver station BTS after the setup.

Fifth Embodiment

This embodiment is a configuration example for performing the processesin the first to fourth embodiments with a scheduler, and FIG. 18 shows acorresponding configuration example of base transceiver station BTS.FIG. 19 is a process sequence flow of the fifth embodiment.

When receiving a connection setting request from the radio networkcontroller RNC (step S1), the base transceiver station BTS selects theutilized frame format in the scheduler unit 38 as is the case with, forexample, the first embodiment, such that such that the transmissionpower peak is reduced after the user- or service-multiplexing (step S2d), and the result is notified to the terminal MS (step S3).

That is, for the terminals MS capable of the transmission, thepriorities of the transmission is calculated based on the channelquality information (e.g., CQI or SIR) returned from the terminals MS,for example. This result is used to select which terminal thetransmission is performed for and the scheduler unit 38 selects themodulating method such as QPSK, the transmission data size, the utilizedframe format, and the encoding rate or encoding method (method ofpuncture, repetition, etc.) (step Std).

The control signal is generated from the selected result and transmittedto the terminal MS (step S3). The same processes as the first embodiment(steps S4 to S6) are subsequently performed. In this way, the sameeffects as the first embodiment are generated.

During the connection, the scheduler unit 38 calculates priorities ofthe transmission to perform scheduling and monitors the peaktransmission power at the same time, and if the scheduler unit 38determines that the utilized frame format is needed to be changed, theutilized frame format after the change is also notified to the terminalMS.

The terminal subsequently performs the same process as the firstembodiment to change the utilized frame format.

In this way, the same effects as the first embodiment are generated. Ifthe change is not made, “no change” or “maintaining (or keeping) thestatus quo” may be transmitted.

Sixth Embodiment

In the fifth embodiment, the utilized frame format is selected at thetime of the connection setup and the utilized frame format is changed bythe scheduler unit capable of formatting.

On the other hand, in a sixth embodiment, the terminals MS are groupedfor each frame format and the scheduling is performed for each group.

Specifically, as shown in FIG. 20 describing the sixth embodiment, theterminals are grouped for each utilized frame format. The scheduler unit38 is constituted by a plurality of schedulers corresponding torespective groups.

In FIG. 20:

Scheduler 1 (using format 1), terminals MS100 to MS 109

Scheduler 2 (using format 2), terminals MS110 to MS 119

Scheduler 3 (using format 3), terminals MS120 to MS 129

Scheduler 4 (using format 4), terminals MS130 to MS 139

For example, the scheduler 1 prioritizes the transmission based on theCQI of the terminals MS100 to MS 109 and selects the terminal MS 101having the highest priority.

The scheduler 2 prioritizes the transmission based on the CQI of theterminals MS110 to MS 119 and selects the terminal MS 112 having thehighest priority.

The scheduler 3 prioritizes the transmission based on the CQI of theterminals MS120 to MS 129 and selects the terminal MS 122 having thehighest priority.

The scheduler 4 prioritizes the transmission based on the CQI of theterminals MS130 to MS 139 and selects the terminal MS 133 having thehighest priority.

For each selected terminal MS, the modulation mode, data size, encodingrate, etc. are selected as described above, and the control signal isgenerated and transmitted to the corresponding terminal MS. The data foreach terminal are then multiplexed and the data are transmitted to eachterminal. Each format is combined such that the transmission power peakis reduced after the multiplexing.

Although one terminal is selected in each of the four groups, theterminal can be selected in any manner as long as the transmission powerpeak is reduced after the multiplexing.

In the above description, the grouping is performed based on theselected frame formats. However, if the utilized frame format is changedas described above, the groups can be changed in accordance with thechanged frame formats to perform the same process.

Specifically, it is assumed that the utilized frame format of oneterminal MSi is the frame format 1 at the time of the connection setupand that the terminal MSi belongs to the group of the scheduler 1. It isalso assumed that the utilized frame format is changed to reduce thepeak transmission power and that the frame format 2 is to be utilized.In this case, the terminal MSi is migrated from the group of thescheduler 1 to the group of the scheduler 2 and if the utilized frameformat is not needed to be changed in the same way, the terminal MSibelongs to that group.

By performing the above process, the same effects as the firstembodiment are generated.

Seventh Embodiment

The present invention has an aspect of a method of notifying theutilized frame format information, and in the first to sixthembodiments, the selected frame format information is symbolized andtransmitted as follows.

Numbers are added to the frame formats and the numbers are defined by,for example, four-bit signals as shown in table 1, which serve asindices indicating the utilized frame formats.

These are used as the control signals from the base transceiver stationBTS to the terminals MS or from the radio network controller RNC to thebase transceiver station BTS and the terminals MS.

The utilized frame format can be set and changed by performing the firstto sixth embodiments and embodiments described later with the use ofthese signals.

If the utilized frame format is not changed, the control signal may betransmitted which is defined as all “0” as shown in table 1, forexample. Although four-bit signals are used in the example of table 1,the signal may have at least three bits.

TABLE 1 Format Control Signal no change 0000 format 1 0001 format 2 0010format 3 0011 format 4 0100

Eighth Embodiment

In this embodiment, when the utilized frame format is changed in thethird embodiment, the transmission power is measured by feeding back thetransmission power at the end of the antenna and the utilized frameformat is changed based on the result thereof.

FIG. 21 is a configuration example of the base transceiver station BTScorresponding to the eighth embodiment. The output power of thetransmission radio unit 34 is measured and/or calculated by atransmission power calculating unit 39. Based on this result, the frameformat controlling unit 36 performs control such that the peaktransmission power is reduced. If it is determined that the format mustbe changed to reduce the peak transmission power, one or more frameformats used by one or more terminals are changed as is the case withthe first embodiment.

In this way, the same effects as the first embodiment are generated.

Ninth Embodiment

In the eighth embodiment, a threshold Ppth is further set in the peaktransmission power. When comparing with the measured peak transmissionpower Pp in the frame format controlling unit, if the peak transmissionpower Pp is greater than the threshold Ppth, the utilized frame formatis changed.

FIG. 22 is a configuration example of the base transceiver station BTScorresponding to a ninth embodiment, FIG. 23 is an example of a processflow of the ninth embodiment; and FIGS. 24 and 25 are process sequences.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pp_th (36a) is set (step S10). The output power of the transmission radio unit 34is calculated by an output power calculating unit 39. The peaktransmission power calculating unit 39 stores the measurement result ofthe output power calculating unit 39, for example, from time T to timeT+t to measure and/or calculate the peak transmission power Pp (stepS11).

The result and the peak transmission power threshold Pp_th are comparedby the frame format controlling unit 36 (step S12) and if the peaktransmission power Pp is greater than the threshold Pp_th (step S12,Yes), it is determined that the utilized frame format is needed to bechanged.

If it is determined that the format is needed to be changed, one or moreframe formats used by one or more terminals are changed such that thepeak transmission power is reduced (step S13).

Specifically, in the sequence flow of FIG. 24, for example, the utilizedframe format is changed for a terminal using the format that has thehighest transmission power at the time of the peak transmission power(step S2 b). Once the terminal to be changed is determined, the terminalis notified of the utilized frame format (step S3). The notifiedterminal changes the setting of the receiving unit (step S4) andtransmits the setting completion notification to the base transceiverstation (step S5).

After receiving the completion notification, the base transceiverstation BTS uses the changed frame format to perform the transmission(step S6).

In this way, the peak transmission power can be reduced and the sameeffects as the first embodiment can be obtained.

As shown in FIG. 25, the terminal MS may not return the settingcompletion notification to the base transceiver station BTS (step S5).Specifically, the change timing is notified along with the frame formatnotification from the base transceiver station BTS to the terminal MS.The terminal receiving the change timing performs the change at theinstructed change timing. In this way, the setting completionnotification can be omitted.

Tenth Embodiment

Although the utilized frame format is controlled using the peaktransmission power in the ninth embodiment, the utilized frame format iscontrolled using the PAPR in this embodiment.

FIG. 26 shows a configuration example of the base transceiver stationcorresponding to a tenth embodiment and FIG. 27 shows the process flowexample thereof.

When the base transceiver station is activated or when the connection isestablished, a PAPR threshold Ppapr_th (36 b) is set (step S20).

The output power of the transmission radio unit 34 is measured andcalculated by the transmission power calculating unit 39. A PAPRcalculating unit 39 b stores the measurement result of the transmissionpower calculating unit 39, for example, from time T to time T+t tocalculate the peak transmission power Pp (step S21) and an averagetransmission power Pave (step S22), which are used to calculate Ppapr(step S23).

The calculation result Ppapr and the PAPR threshold Ppapr_th (26 b) arecompared by the frame format controlling unit 36 (step S24). If thecalculation result Ppapr is greater than the threshold Ppapr_th, it isdetermined that the utilized frame format is needed to be changed (stepS25).

If it is determined that the format is needed to be changed, one or moreframe formats used by one or more terminals are changed such that thePAPR is reduced. Specifically, for example, the utilized frame format ischanged for a terminal MS using the format that has the highesttransmission power at the time of the peak transmission power.

Once the terminal to be changed is determined, the terminal MS isnotified of the utilized frame format. The notified terminal changes thesetting of the receiving unit and transmits the setting completionnotification to the base transceiver station BTS.

After receiving the completion notification, the base transceiverstation BTS uses the changed frame format to perform the transmission.

In this way, the peak transmission power can be reduced; the PAPR isreduced consequently; and the same effects as the first embodiment canbe obtained.

Eleventh Embodiment

In the ninth and tenth embodiments, the frame format control isperformed by the scheduler unit 38.

Description will be made of the case of the ninth embodiment. FIG. 28shows a configuration example of the base transceiver station BTScorresponding to the tenth embodiment.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pp_th (36a) is set.

The output power of the transmission radio unit 34 is calculated by anoutput power calculating unit 39. The peak transmission powercalculating unit 39 b stores the measurement result of the transmissionpower calculating unit 39, for example, from time T to time T+t tocalculate the peak transmission power Pp. The result and the peaktransmission power threshold Pp_th (36 a) are compared by the schedulerunit 38 and if the peak transmission power Pp is greater than thethreshold Pp_th, it is determined that the utilized frame format isneeded to be changed.

If it is determined that the format is needed to be changed, one or moreframe formats used by one or more terminals are changed such that thepeak transmission power is reduced. Specifically, the utilized frameformat is changed for a terminal using the format that has the highesttransmission power at the time of the peak transmission power.

Once the terminal MS to be changed is determined, the terminal MS isnotified of the utilized frame format. The notified terminal MS changesthe setting of the receiving unit and transmits the setting completionnotification to the base transceiver station BTS.

After receiving the completion notification, the base transceiverstation BTS uses the changed frame format to perform the transmission.

In this way, the peak transmission power can be reduced and the sameeffects as the first embodiment can be obtained.

Although the selected format has the highest transmission power in theabove description, the formats having the highest to the predeterminedmth-highest transmission power may be selected to be changed.Alternatively, when the highest transmission power is selected and thetransmission is performed, if the peak transmission power thereof isgreater than the peak power transmission power threshold, the sameprocess is performed. In this way, the process can be repeated until thepeak transmission power becomes lower than the peak transmission powerthreshold.

Twelfth Embodiment

The peak transmission power is reduced for each user or service. FIG. 29shows a configuration example of the base transceiver station BTScorresponding to a twelfth embodiment and FIG. 30 shows an example ofthe process flow thereof.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pue_th(36 a) is set for each user or service (step S30). The output of thetransmission radio unit 34 is subjected to frequency separation for eachuser or service, for example, by a filter (not shown in FIG. 29), andthe transmission power for each user or service is measured orcalculated by a transmission power calculating unit 41. As is the casewith the ninth embodiment, a peak transmission power calculating unit 41a stores the measurement results of the transmission power calculatingunit 41 for the number (=k) of (terminals of) users, for example, fromtime T to time T+t (steps S31 to S33) to calculate the peak transmissionpower Pp (step S34).

Description will be made of the case that the peak power is calculatedfor each user.

The frame format controlling unit 36 compares the calculated peaktransmission power Pue_k for each user with a peak transmission powerthreshold Pue_th (step S35) and if the peak transmission power Pue_k ishigher (step S35, yes), the terminal MSk is notified of the change inthe utilized frame format (step S36). The above process is performed foreach terminal (MS1 to MSk) in communication.

In this way, the peak transmission power of the entire base transceiverstation can be constrained to a lower level. Therefore, the same effectsas the first embodiment can be obtained.

Thirteenth Embodiment

In the twelfth embodiment, the frame format control is performed withthe use of the peak transmission power of the entire base transceiverstation in addition to the peak transmission power for each user orservice.

FIG. 31 shows a configuration example of the base transceiver stationBTS corresponding to a thirteenth embodiment and FIG. 32 shows anexample of the process flow thereof.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pp_th (36a) of the entire base transceiver station BTS and a peak transmissionpower threshold Pue_th (36 b) for each user or service are set (stepsS40, S41). Since the service may be different for the same user, theservice and the user are not in a dependent relationship.

Description will be made of an example of the user case.

The output of the transmission radio unit 34 is measured by the outputpower calculating unit 39 to measure and calculate the transmissionpower of the entire base transceiver station BTS. This is repeated for acertain period to calculate the peak transmission power of the basetransceiver station BTS.

In parallel with these processes, the output of the base transceiverstation transmission radio unit 34 is subjected to frequency separationfor each user, for example, by a filter (not shown in FIG. 32), and thetransmission power for each user is measured and calculated by thetransmission power calculating unit 39. This is performed for a certainperiod as is the case with the ninth embodiment and the peaktransmission power Pp is calculated by a peak transmission powercalculating unit 39 a (step S42).

These pieces of information are delivered to the frame formatcontrolling unit 36.

The frame format controlling unit 36 compares the peak transmissionpower Pp of the entire base transceiver station with a peak transmissionpower threshold Pue_th of the entire base transceiver station (step S43)and if the peak transmission power Pp is higher (step S43, yes), it isdetermined that the utilized frame format is needed to be changed (stepS49).

If it is determined that the format is needed to be changed, a peaktransmission power Pue_k for each user is compared with a peaktransmission power threshold Pue_th for each user (steps S44 to S48) andif the peak transmission power Pue_k is higher (step S48, yes), theutilized frame format of the terminal MSk is changed (step S49). Thisprocess is performed for each terminal (MS1 to MSk).

Only the frame format used by one user may be changed if the peaktransmission power of the entire base transceiver station BTS can beconstrained to a lower level that is equal to or less than thethreshold.

In this way, the peak transmission power of the entire base transceiverstation can be constrained to a lower level. Therefore, the same effectsas the first embodiment can be obtained.

The comparison between the peak transmission power Pp of the entire basetransceiver station amd the peak transmission power threshold Pue_th maybe performed concurrently with the comparison between the peaktransmission power Pue_k for each user and the peak transmission powerthreshold Pue_th for each user.

Fourteenth Embodiment

In the first to thirteenth embodiments, the peak transmission power hasbeen calculated from the output of the transmission radio unit 34. Inthis embodiment, the peak transmission power is calculated based on abase band signal, for example, the output of the modulating unit 33.

FIG. 33 shows a configuration example of the base transceiver stationcorresponding to a fourteenth embodiment and the process flow thereof isthe same as the fifth embodiment.

In the transmission power control of the current mobile communicationsystem, the transmission power is typically controlled by performing theamplitude control of the base band signal because of easiness of thecontrol. Therefore, in the fourteenth embodiment, description will bemade of the case that the transmission power control of the aboveembodiment is applied to the base band signal.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pbb_th(36 e) is set.

The output power of the modulating unit 33 is measured and calculated bythe transmission power calculating unit 39. Specifically, the base bandsignal power is calculated from the output of the modulating unit 33,i.e., the base band signal, and the transmission power is calculatedfrom the gain of the transmission radio unit 34 at the time. The peaktransmission power Pbb is calculated from these results for a certainperiod.

The peak transmission power Pbb and the threshold Pbb_th are compared bythe frame format controlling unit 36 and if the peak transmission poweris higher, it is determined that the utilized frame format is needed tobe changed.

The frame format controlling unit 36 selects the terminal where theutilized frame format is changed, to which the frame format after thechange is notified. In the method of selecting the terminal MS, forexample, the selected terminal MS may be a terminal that has the highesttransmission power when the transmission power reaches a peak.

The same process as the fifth embodiment is performed subsequently. Inthis way, the peak transmission power of the entire base transceiverstation can be constrained to a lower level. Therefore, the same effectsas the first embodiment can be obtained.

Although the transmission power is estimated in the above description,the control may be performed directly from the power of the base bandsignal. Although the output of the modulating unit is used, theintermediate frequency (IF) may be used and a signal before modulationmay also be used.

Fifteenth Embodiment

In the twelfth embodiment, the utilized frame format is controlled withthe base band signal as is the case with the fourteenth embodiment.

FIG. 34 shows a configuration example of a base transceiver station BTScorresponding to a fifteenth embodiment. When the base transceiverstation BTS is activated or when the connection is established, a peaktransmission power threshold 36 b is set for each user or service.

The output of the base transceiver station modulating unit 33 issubjected to frequency separation for each user or service, for example,by a filter (not shown in FIG. 34), and the transmission power for eachuser or service is calculated by the transmission power calculating unit41. This is performed for a certain period as is the case with the ninthembodiment and the peak transmission power is calculated by the peaktransmission power calculating unit 41 a.

Description will be made of the case that the peak power is calculatedfor each user. The frame format controlling unit 36 compares thecalculated peak transmission power Pue_k for each user with a peaktransmission power threshold Pue_th. If the peak transmission powerPue_k is higher, the terminal MSk is notified of the change in theutilized frame format. The above process is performed for each terminalMS1 to MSk in communication.

In this way, the peak transmission power of the entire base transceiverstation BTS can be constrained to a lower level. Therefore, the sameeffects as the first embodiment can be obtained. As is the case with thefourteenth embodiment, the transmission power may be measured andcalculated with the use of the output power of the modulating unit 33and the gain of the transmission radio unit 34, and the control may beperformed directly from the power of the base band signal.

Sixteenth Embodiment

In the thirteenth embodiment, the process is performed with the baseband signal as is the case with the fourteenth and fifteenth embodiment.

FIG. 35 shows a configuration example of the base transceiver stationBTS corresponding to a sixteenth embodiment and the process flow thereofis the same as the thirteenth embodiment.

When the base transceiver station BTS is activated or when theconnection is established, a peak transmission power threshold Pp_th ofthe entire base transceiver station and a peak transmission powerthreshold for each user or service are set. Since the service may bedifferent for the same user, the service and the user are not in adependent relationship.

Description will be made of an example of the user case.

The output of the base transceiver station modulating unit 33 ismeasured by the output power calculating unit 41, and the transmissionpower of the entire base transceiver station is calculated with the useof the result thereof, the gain of the transmission radio unit 34, etc.This is repeated for a certain period to calculate the peak transmissionpower of the base transceiver station. In parallel with these processes,the output of the base transceiver station modulating unit is subjectedto frequency separation for each user, for example, by a filter (notshown in FIG. 35), and the transmission power for each user is measuredand calculated by the transmission power calculating unit 41. Thetransmission power for each user is calculated with the use of theresult thereof, the gain of the transmission radio unit 34, etc. This isperformed for a certain period as is the case with the ninth embodimentand the peak transmission power is calculated by the peak transmissionpower calculating unit 41 a.

These pieces of information are delivered to the frame formatcontrolling unit 36.

The frame format controlling unit 36 compares the peak transmissionpower Pp of the entire base transceiver station BTS with the peaktransmission power threshold Pue_th of the entire base transceiverstation and if the peak transmission power is higher, it is determinedthat the utilized frame format is needed to be changed.

If it is determined that the format is needed to be changed, the peaktransmission power Pue_k for each user is compared with the peaktransmission power threshold Pue_th for each user and if the peaktransmission power Pue_k is higher, the utilized frame format of theterminal MSk is changed. This process is performed for each terminal.

Only the frame format used by one user may be changed if the peaktransmission power of the entire base transceiver station BTS can beconstrained to a lower level that is equal to or less than thethreshold. In this way, the peak transmission power of the entire basetransceiver station can be constrained to a lower level. Therefore, thesame effects as the first embodiment can be obtained.

As is the case with the fourteenth embodiment, the transmission powermay be calculated with the use of the output power of the modulatingunit 33 and the gain of the transmission radio unit 34, and the controlmay be performed directly from the power of the base band signal.

While the illustrative and presently preferred embodiments of thepresent invention have been described in detail herein, it is to beunderstood that the inventive concepts may be otherwise variouslyembodied and employed and that the appended claims are intended to beconstrued to include such variations except insofar as limited by theprior art.

1. A radio communication system wherein one or a consecutive pluralityof sub-carriers at certain frequency intervals form sub-carrier groupseach of which is assigned to a different user, the radio communicationsystem comprising: a radio communication apparatus; and a terminalconfigured to receive a notification for identifying control signalpositions from the radio communication apparatus, wherein the terminalreceives a control signal and a data signal according to the controlsignal positions identified by the notification.
 2. The radiocommunication system according to claim 1, wherein the sub-carriers areassigned by using a distributed OFDMA (Orthogonal Frequency DivisionMultiplexing Access).
 3. A terminal for use in a radio communicationsystem wherein one or a consecutive plurality of sub-carriers at certainfrequency intervals form sub-carrier groups each of which is assigned toa different user, the terminal comprising: a receiver configured toreceive a notification for identifying control signal positions, whichis controlled for each user and notified to each terminal from a radiocommunication apparatus and receive a control signal and a data signalaccording to the control signal positions identified by the notificationon the sub-carrier group.
 4. A radio communication method used in aradio communication system wherein one or a consecutive plurality ofsub-carriers at certain frequency intervals form sub-carrier groups eachof which is assigned to a different user, the radio communication methodcomprising: controlling, by a radio communication apparatus, signalpositions of a control signal and a data signal on a sub-carrier groupfor each user; transmitting a notification for identifying controlsignal positions to terminals from the radio communication apparatus;and receiving, by a terminal a control signal and a data signal on thesub-carrier from the radio communication apparatus according to thecontrol signal positions identified by the notification.
 5. A radiocommunication apparatus used in a radio communication system wherein oneor a consecutive plurality of sub-carriers frequency intervals formsub-carrier groups each of which is assigned to a different user, theradio communication apparatus comprising: a generator configured togenerate a notification of a control signal position; and a transmitterconfigured to transmit to a terminal, a notification for identifyingcontrol signal positions, and a control signal and a data signal, whichare set on a sub-carrier group, as corresponding to the control signalpositions identified by the notification.